The present invention relates to an apparatus and a method for conducting a process such as etching, ashing and depositing on a semiconductor substrate or an LCD glass plate by plasma generated by using microwave energy.
Plasma generated by externally applying an energy to a reaction gas is widely used in manufacture processes for LSIs and LCDs. In particular, the usage of plasma is an indispensable basic technique in a dry etching process and chemical vapor deposition.
FIG. 1 is a side sectional view of a conventional microwave plasma process apparatus and FIG. 2 is a plan view of the plasma process apparatus of FIG. 1. A reactor 31 in the shape of a rectangular box is made from aluminum. The reactor 31 is provided with a microwave introducing window at its upper portion, and the microwave introducing window is airtightly sealed with a sealing plate 34. The sealing plate 34 is made from a dielectric material, such as quartz glass and alumina, having heat resistance, microwave penetrability and a small dielectric loss.
The reactor 31 is coupled with a cover 40 in the shape of a rectangular box covering the upper portion of the reactor 31. A dielectric plate 41 is disposed on the ceiling within the cover 40, and an air gap 43 is provided between the dielectric plate 41 and the sealing plate 34. The dielectric plate 41 is formed out of a plate of a dielectric material, for example, a fluororesin such as Teflon (registered trademark), a polyethylene resin or a polystyrene resin in a substantially pentagonal shape, obtained by combining a rectangle and a triangle, provided with a projection on its apex. The projection on the apex of the dielectric plate 41 is fit in a waveguide 21 coupled with the cover 40. The waveguide 21 is connected with a microwave oscillator 20, so that a microwave oscillated by the microwave oscillator 20 can be guided by the waveguide 21 so as to enter the projection of the dielectric plate 41.
As described above, the base portion of the projection of the dielectric plate 41 is formed as a taper portion 41a in a substantially triangle shape in a plan view. The microwave having entered the projection is expanded in the lateral direction along the taper portion 41a and propagated in the entire dielectric plate 41. The microwave is reflected on the end face of the cover 40 opposing the waveguide 21, so that the incident wave and the reflected wave can be superimposed so as to generate a standing wave in the dielectric plate 41.
The inside of the reactor 31 works as a process chamber 32, and a desired gas is introduced into the process chamber 32 through a gas inlet tube 35. At the center of the bottom of the process chamber 32, a table 33 for placing a sample W is disposed, and the table 33 is connected through a matching box 36 with a high frequency power supply 37. The bottom of the reactor 31 is also provided with an air outlet 38, so as to exhaust the air within the process chamber 32 through the air outlet 38.
In conducting an etching process on the surface of the sample W by using this microwave plasma process apparatus, the pressure within the process chamber 32 is decreased down to a desired pressure by exhausting through the air outlet 38, and then, a reaction gas is supplied to the process chamber 32 through the gas inlet tube 35. Subsequently, a microwave is oscillated by the microwave oscillator 20, and the oscillated microwave is introduced into the dielectric plate 41 through the waveguide 21. At this point, the microwave is uniformly expanded within the dielectric plate 41 owing to the taper portion 41a, thereby generating a standing wave in the dielectric plate 41. This standing wave forms a leakage electric field below the dielectric plate 41, and the leakage electric field is introduced into the process chamber 32 through the air gap 43 and the sealing plate 34. In this manner, the microwave is propagated to the process chamber 32. As a result, plasma is generated in the process chamber 32, and the surface of the sample W is etched by using the plasma.
The conventional microwave plasma process apparatus includes the taper portion 41a projecting from the edges of the sealing plate 34 and the reactor 31 in the horizontal direction in order to uniformly expand the microwave in the dielectric plate 41. The dimension of the taper portion 41a is defined in accordance with the area of the dielectric plate 41, namely, the dimension of the process chamber 32. Accordingly, when the conventional microwave plasma process apparatus is to be installed, an additional horizontally extending space is required for the taper portion 41a projecting from the edge of the reactor 31.
In accordance with the dimensional increase of the sample W, there is a demand for a microwave plasma process apparatus including the reactor 31 with a further larger dimension. At the same time, there is a demand that the entire apparatus can be installed in a space as small as possible. However, since the dimension of the taper portion 41a of the conventional apparatus is defined in accordance with the dimension of the reactor 31, the dimension of the taper portion 41a increases as the dimension of the reactor 31 increases. Accordingly, the two demands that a microwave plasma process apparatus including a larger reaction vessel 31 is to be installed in a space as small as possible cannot be satisfied at the same time.